Electron-neutron scattering and transport properties of neutron stars

TL;DR

This paper investigates how electrons in neutron stars interact with neutrons, affecting their transport properties like conductivity and viscosity, especially under certain phases of matter, which was previously underexplored.

Contribution

It introduces a detailed calculation of electron-neutron interactions in neutron stars and assesses their impact on transport properties, highlighting scenarios where this interaction dominates.

Findings

Electron-neutron scattering can significantly influence shear viscosity.

Electron-neutron interactions can surpass other scattering mechanisms in certain phases.

Transport properties are notably affected when protons are superconducting and neutrons are normal.

Abstract

We show that electrons can couple to the neutron excitations in neutron stars and find that this can limit their contribution to the transport properties of dense matter, especially the shear viscosity. The coupling between electrons and neutrons is induced by protons in the core, and by ions in the crust. We calculate the effective electron-neutron interaction for the kinematics of relevance to the scattering of degenerate electrons at high density. We use this interaction to calculate the electron thermal conductivity, electrical conductivity, and shear viscosity in the neutron star inner crust, and in the core where we consider both normal and superfluid phases of neutron-rich matter. In some cases, particularly when protons are superconducting and neutrons are in their normal phase, we find that electron-neutron scattering can be more important than the other scattering mechanisms considered previously.